Ceramics and ceramic composites have been utilized as refractory materials in a number of different applications. It has been found that ceramic and ceramic composite refractories can be used as many different components for applications which require, among other things, good resistance to thermal shock, good corrosion, abrasion and erosion resistance, etc. For example, ceramic and ceramic composite materials have been utilized as liners in molten glass furnaces and molten metal furnaces, as well as in apparatus associated with such furnaces (e.g., apparatus which direct or constrict the flow of molten fluids from one point to another).
Exemplary uses for ceramic materials in molten metal furnace and molten metal transfer systems include furnace linings, slide gates, submerged entry nozzles, ladle shrouds, tundishes, tap hole liners, etc. Many metal manufacturing processes (including steel manufacturing processes) have recently been changed from traditional batch processes to some type of continuous casting process for reasons of economy and productivity. However, these continuous processing methods place extreme requirements upon the materials which are in contact with the static or flowing molten materials. For example, in the steel industry, slide gate systems, which are used for controlling the flow of molten metal from a large chamber (e.g., a furnace, ladle or tundish) into a smaller chamber (e.g., a mold), have been known for many years. However, only recently certain materials have been manufactured to meet the necessary mechanical/physical requirements imposed by such systems. Generally, slide gate systems include some type of rotating or sliding design which consists of, for example, a fixed nozzle attached to and within a moveable plate. The flow of molten metal from a ladle is controlled by moving the moveable plate to fully or partially aligned openings. When filling the ladle, and during shut off, the openings are misaligned. The advantage which stems from the use of a slide gate in continuous metal casting is that the conventional stopper rod system is eliminated. Specifically, in conventional stopper rod systems difficulties were encountered in stopping and/or modulating molten metal flow through an opening. Often the conventional stopper rod systems were not completely successful in terminating the flow of molten metal therethrough. However, even though slide gate systems have been achieving great successes in improving continuous casting of molten metals, the stringent requirements placed upon the materials for use as slide gates have resulted in many problems for the material design engineer. Accordingly, the need for new and better materials continues.
To date, common materials for use in slide gate systems include tar-impregnated alumina materials, fired-magnesia materials, etc. However, these materials suffer from many material deficiencies such as, for example, certain metals may corrode the bonding media or matrix which is utilized to hold together the refractory. Additionally, conventional materials may not possess the desired combination of thermal shock resistance, corrosion resistance, erosion resistance, abrasion resistance, and/or strength which permit the materials to function for a sufficient amount of time to achieve the economies and efficiencies needed in modern manufacturing operations. Accordingly, a need exists to develop a material which exhibits corrosion resistance, erosion resistance, thermal shock resistance, abrasion resistance, sufficient strength, etc., to withstand the severe environment to which such materials are exposed in molten metals operations.
Similar corrosion, erosion, abrasion, thermal shock, etc., problems exist in the continuous manufacture of glasses. Specifically, glasses typically contain highly corrosive media (e.g., calcia, soda, magnesia, fluorides, chlorides, etc.) which may attack even the best ceramic materials. Moreover, glass producing operations also create severe thermal shock conditions as well as highly erosive and abrasive conditions. Accordingly, the material engineer is also faced with difficult material design/fabrication problems in designing materials for use in the glass industry.
The present invention satisfies the above-discussed needs by providing materials which are useful in metal production and glass production industries. Specifically, the materials of the present invention can be used as refractories for direct contact with, for example, molten steel, molten aluminum, molten copper, molten bronze, molten iron, certain molten glasses, etc. Moreover, the refractory materials of the present invention have substantial erosion and abrasion resistance which permit, in many applications, the refractory materials to be in direct contact with each other and to be in sliding engagement with at least a portion of another surface of another refractory material (e.g., moveable parts of a slide gate or portions thereof for use in molten steel applications).
The subject matter of this application is related to that of several Commonly Owned Patents and Commonly Owned and Copending Patent Applications. Particularly, these Patents and Patent Applications describe novel methods for making ceramic and ceramic matrix composite materials (hereinafter sometimes referred to as "Commonly Owned Ceramic Matrix Patent Applications and Patents").
A novel approach to the formation of ceramic materials is disclosed generically in Commonly Owned U.S. Pat. No. 4,713,360, which issued on Dec. 15, 1987, in the names of Marc S. Newkirk et al. and entitled "Novel Ceramic Materials and Methods for Making Same". This Patent discloses a method of producing self-supporting ceramic bodies grown as the oxidation reaction product of a molten parent precursor metal which is reacted with a vapor-phase oxidant to form an oxidation reaction product. Molten metal migrates through the formed oxidation reaction product to react with the oxidant thereby continuously developing a ceramic polycrystalline body which can, if desired, include an interconnected metallic component. The process may be enhanced by the use of one or more dopants alloyed with the parent metal. For example, in the case of oxidizing aluminum in air, it is desirable to alloy magnesium and silicon with the aluminum to produce alpha-alumina ceramic structures. This method was improved upon by the application of dopant materials to the surface of the parent metal, as described in Commonly Owned U.S. Pat. No. 4,853,352, which issued on Aug. 1, 1989, in the names of Marc S. Newkirk et al., and entitled "Methods of Making Self-Supporting Ceramic Materials", a European counterpart to which was published in the EPO on Jan. 22, 1986.
A novel method for producing a self-supporting ceramic composite by growing an oxidation reaction product from a parent metal into a permeable mass of filler is disclosed in commonly owned and copending U.S. patent application Ser. No. 08/007,387, filed Jan. 21, 1993, which is a continuation of U.S. patent application Ser. No. 07/811,895, filed Dec. 20, 1991 (and now abandoned), which was a continuation of U.S. patent application Ser. No. 07/433,733, filed Nov. 30, 1989 (and now abandoned), and entitled "Method of Making Composite Articles Having Embedded Filler", which was a continuation-in-part of U.S. patent application Ser. No. 07/415,180, filed Sep. 29, 1989 (and now abandoned), which was a divisional of U.S. Pat. No. 4,916,113, issued Apr. 10, 1990, and entitled "Methods of Making Composite Articles Having Embedded Filler", which is a continuation of U.S. Pat. No. 4,851,375, issued Jul. 25, 1989, and entitled "Composite Ceramic Articles and Methods of Making the Same", all in the names of Marc S. Newkirk, et al.
A method for producing ceramic composite bodies having a predetermined geometry or shape is disclosed in Commonly Owned U.S. Pat. No. 5,017,526, which issued on May 21, 1991, in the names of Marc S. Newkirk et al., a European counterpart to which was published in the EPO on Jan. 22, 1986. In accordance with the method in this U.S. Patent, the developing oxidation reaction product infiltrates a permeable preform of filler material in a direction towards a defined surface boundary.
It was discovered that high fidelity is more readily achieved by providing the preform with a barrier means, as disclosed in Commonly Owned U.S. Pat. No. 5,236,786, which issued on Aug. 17, 1983, entitled "Shaped Ceramic Composites with a Barrier," which is a continuation of U.S. patent application Ser. No. 07/295,488, filed Jan. 10, 1989 (and now abandoned), which was a continuation of U.S. Pat. No. 4,923,832, which issued May 8, 1990, all in the names of Marc S. Newkirk et al., a European counterpart to which was published in the EPO on Nov. 11, 1987. This method produces shaped self-supporting ceramic bodies, including shaped ceramic composites, by growing the oxidation reaction product of a parent metal to a barrier means spaced from the metal for establishing a boundary or surface.
Ceramic composites having a cavity with an interior geometry inversely replicating the shape of a positive mold or pattern are disclosed in Commonly Owned U.S. Pat. No. 5,275,987, which issued on Jan. 4, 1994, which is a continuation of U.S. Pat. No. 5,168,081, which issued on Dec. 1, 1992, which is a continuation of U.S. Pat. No. 5,051,382, which issued Sep. 24, 1991, which is a divisional of U.S. Pat. No. 4,828,785, which issued May 9, 1989, all in the names of Marc S. Newkirk, et al., and each entitled "Inverse Shape Replication Method of Making Ceramic Composite Articles and Articles Obtained Thereby," a European counterpart to which was published in the EPO on Sep. 2, 1987; and in Commonly Owned U.S. Pat. No. 5,212,124, which issued on May 18, 1993, which is a continuation of U.S. patent application Ser. No. 07/308,420, filed Feb. 8, 1989 (and now abandoned), which was a continuation of U.S. Pat. No. 4,859,640, which issued on Aug. 22, 1989, all in the names of Marc S. Newkirk et al. and entitled "Method of Making Ceramic Composite Articles with Shape Replicated Surfaces and Articles Obtained Thereby," a European counterpart to which was published in the EPO on Mar. 9, 1988.
The feeding of additional molten parent metal from a reservoir has been successfully utilized to produce thick ceramic matrix composite structures. Particularly, as disclosed in Commonly Owned U.S. Pat. No. 4,918,034, issued Apr. 17, 1990, which is a continuation-in-part of U.S. Pat. No. 4,900,699, issued Feb. 13, 1990, both in the names of Marc S. Newkirk et al., and entitled "Reservoir Feed Method of Making Ceramic Composite Structures and Structures Made Thereby", a European counterpart to which was published in the EPO on Mar. 30, 1988, the reservoir feed method has been successfully applied to form ceramic matrix composite structures. According to the method of this Newkirk et al. invention, the ceramic or ceramic composite body which is produced comprises a self-supporting ceramic composite structure which includes a ceramic matrix obtained by the oxidation reaction of a parent metal with an oxidant to form a polycrystalline material. In conducting the process, a body of the parent metal and a permeable filler are oriented relative to each other so that formation of the oxidation reaction product will occur in a direction toward and into the filler. The parent metal is described as being present as a first source and as a reservoir, the reservoir of metal communicating with the first source due to, for example, gravity flow. The first source of molten parent metal reacts with the oxidant to begin the formation of the oxidation reaction product. As the first source of molten parent metal is consumed, it is replenished, preferably by a continuous means, from the reservoir of parent metal as the oxidation reaction product continues to be produced and infiltrates the filler. Thus, the reservoir assures that ample parent metal will be available to continue the process until the oxidation reaction product has grown to a desired extent.
A method for tailoring the constituency of the metallic component of a ceramic matrix composite structure is disclosed in Commonly Owned U.S. Pat. No. 5,017,533, issued on May 21, 1992, which in turn was a continuation of U.S. patent application Ser. No. 06/908,454, filed Sep. 17, 1986 (and now abandoned), both of which are in the names of Marc S. Newkirk et al., and entitled "Method for In Situ Tailoring the Metallic Component of Ceramic Articles and Articles Made Thereby".
Moreover, U.S. Pat. No. 5,066,618, issued on Nov. 19, 1991, which was a continuation of U.S. patent application Ser. No. 07/269,152, filed Nov. 9, 1988 (and now abandoned), which in turn was a continuation of U.S. Pat. No. 4,818,734, which issued on Apr. 4, 1989, in the names of Robert C. Kantner et al., which was a continuation-in-part of the above-mentioned U.S. patent application Ser. No. 06/908,454, having the same title and also being Commonly Owned. These Patents and the above-mentioned U.S. patent application Ser. No. 06/908,454, disclose methods for tailoring the constituency of the metallic component (both isolated and interconnected) of ceramic and ceramic matrix composite bodies during formation thereof to impart one or more desirable characteristics to the resulting body. Thus, desired performance characteristics for the ceramic or ceramic composite body are advantageously achieved by incorporating the desired metallic component in situ, rather than from an extrinsic source, or by post-forming techniques.
Further, U.S. Pat. No. 5,268,339, which issued on Dec. 7, 1993, was a continuation-in-part of U.S. Pat. No. 5,185,303, which issued on Feb. 9, 1993, which was a continuation of the above-mentioned U.S. Pat. No. 5,066,618. U.S. Pat. No. 5,268,339 discloses a method for forming one or more reaction products in a ceramic matrix composite body subsequent to substantially complete infiltration of a filler material or preform with an oxidation reaction product. In particular, one or more "second materials" are added to the permeable mass. The second materials are substantially non-reactive during infiltration of oxidation reaction product into the permeable mass, but react at higher temperatures subsequent to infiltration to form the other reaction product(s).
As discussed in these Commonly Owned Ceramic Matrix Patent Applications and Patents, novel polycrystalline ceramic materials or polycrystalline ceramic composite materials are produced by the oxidation reaction between a parent metal and an oxidant (e.g., a solid, liquid and/or a gas). In accordance with the generic process disclosed in these Commonly Owned Ceramic Matrix Patent Applications and Patents, a parent metal (e.g., aluminum) is heated to an elevated temperature above its melting point but below the melting point of the oxidation reaction product (e.g., aluminum nitride) to form a body of molten parent metal which reacts upon contact with an oxidant (e.g., a nitrogenous atmosphere) to form the oxidation reaction product. At this temperature, the oxidation reaction product, or at least a portion thereof, is in contact with and extends between the body of molten parent metal and the oxidant, and molten metal is drawn or transported through the formed oxidation reaction product and towards the oxidant. The transported molten metal forms additional fresh oxidation reaction product when contacted with the oxidant, at the surface of previously formed oxidation reaction product. As the process continues, additional metal is transported through this formation of polycrystalline oxidation reaction product thereby continually "growing" a ceramic structure of interconnected crystallites. The resulting ceramic body may contain metallic constituents, such as non-oxidized constituents of the parent metal, and/or voids. Oxidation is used in its broad sense in all of the Commonly Owned Ceramic Matrix Patent Applications and Patents and in this application, and refers to the loss or sharing of electrons by a metal to an oxidant which may be one or more elements and/or compounds. Accordingly, elements other than oxygen may serve as an oxidant.
In certain cases, the parent metal may require the presence of one or more dopants in order to influence favorably or to facilitate growth of the oxidation reaction product. Such dopants may at least partially alloy with the parent metal at some point during or prior to growth of the oxidation reaction product. For example, in the case of aluminum as the parent metal and nitrogen as the oxidant, dopants such as strontium, silicon, nickel and magnesium, to name but a few of a larger class of dopant materials, can be alloyed with aluminum, and the created growth alloy is utilized as the parent metal. The resulting oxidation reaction product of such a growth alloy, in the case of using nitrogen as an oxidant, comprises aluminum nitride.
Novel ceramic composite structures and methods of making the same are also disclosed and claimed in certain of the aforesaid Commonly Owned Ceramic Matrix Patent Applications and Patents which utilize the oxidation reaction to produce ceramic composite structures comprising a substantially inert filler (note: in some cases it may be desirable to use a reactive filler, e.g., a filler which is at least partially reactive with the advancing oxidation reaction product and/or parent metal) infiltrated by the polycrystalline ceramic matrix. A parent metal is positioned adjacent to a mass of permeable filler (or a preform) which can be shaped and treated to be self-supporting, and is then heated to form a body of molten parent metal which is reacted with an oxidant, as described above, to form an oxidation reaction product. As the oxidation reaction product grows and infiltrates the adjacent filler material, molten parent metal is drawn through previously formed oxidation reaction product within the mass of filler and reacts with the oxidant to form additional fresh oxidation reaction product at the surface of the previously formed oxidation reaction product, as described above. The resulting growth of oxidation reaction product infiltrates or embeds the filler and results in the formation of a ceramic composite structure of a polycrystalline ceramic matrix embedding the filler. As also discussed above, the filler (or preform) may utilize a barrier means to establish a boundary or surface for the ceramic composite structure.
Novel processing techniques, and the novel bodies which are produced thereby, are disclosed in Copending and Commonly Owned U.S. patent application Ser. No. 07/902,515, filed on Jun. 22, 1992, which is a continuation-in-part of U.S. Pat. No. 5,215,666, which issued on Jun. 1, 1993, which is a continuation of U.S. patent application Ser. No. 07/763,476, filed on Sep. 20, 1991 (and now abandoned), which was a continuation of U.S. patent application Ser. No. 07/414,198, filed on Sep. 28, 1989 (and now abandoned), which in turn was a continuation of U.S. Pat. No. 4,874,569, which issued on Oct. 17, 1989, all of which are in the names of Jack A. Kuszyk et al., and are entitled "Ceramic Composite and Methods of Making The Same." These patents and patent applications disclose the importance of utilizing an aluminium parent metal alloy containing at least about 1 weight percent zinc for the formation of ceramic composite bodies which are used as refractory bodies.
Thus, the aforesaid Commonly Owned Ceramic Matrix Patent Applications and Patents describe the production of oxidation reaction products which are readily grown to desired sizes and thicknesses heretofore believed to be difficult, if not impossible, to achieve with conventional ceramic processing techniques.